Optical switch and optical waveform monitoring device utilizing optical switch

Abstract

The polarization direction of an optical signal is changed by a polarization controller so as to be orthogonal to a main axis of a polarizer. A control pulse generator generates control pulses from control beam with a wavelength which is different from the wavelength of the optical signal. The optical signal and the control pulse are input to a nonlinear optical fiber. In the nonlinear optical fiber, the optical signal, during a time period in which the optical signal and the control pulse coincide, is amplified with optical parametric amplification around a polarization direction of the control pulse. The optical signal, during the time period in which the optical signal and the control pulse coincide, passes through the polarizer.

1. An optical switch, comprising:
 a first polarization controller to control a polarization direction of a phase-modulated optical signal or a frequency-modulated optical signal; 
 a nonlinear optical medium to which the optical signal output from said first polarization controller is input; 
 an optical pulse generator to generate a control pulse with a wavelength different from that of the optical signal and to provide the control pulse to said nonlinear optical medium; 
 a second polarization controller, placed between said optical pulse generator and said nonlinear optical medium, to align a polarization direction of the control pulse to a designated angle relative to the polarization direction of the optical signal; and 
 a polarizer, placed at the output side of said nonlinear optical medium, having a main polarization axis orthogonal to a polarization direction of the optical signal output from said nonlinear optical medium, 
 the optical signal being selectively amplified with parametric amplification by the control pulse around a polarization direction of the control pulse in said nonlinear optical medium, an angle between the polarization direction of the optical signal and the polarization direction of the control pulse being between 40 and 50 degrees. 
 
     
     
       2. The optical switch according to  claim 1 , wherein the optical signal is an RZ phase-modulated optical signal or an RZ frequency-modulated optical signal. 
     
     
       3. The optical switch according to  claim 2 , wherein the control pulse maintains a constant intensity during a pulse width where the optical power of the optical signal is above a predetermined value. 
     
     
       4. The optical switch according to  claim 2 , wherein the pulse width of the control pulse is shorter than a pulse width in which the optical power of the optical signal is above a predetermined value. 
     
     
       5. A optical switch, comprising:
 a nonlinear optical medium, to which both a phase-modulated optical signal or a frequency-modulated optical signal with a designated polarization direction, and a control pulse with a different wavelength and different polarization direction from the optical signal are input, to change a polarization of the optical signal by cross-phase modulation during a period where the optical signal coincides with the control pulse in the time domain, and to selectively amplify the optical signal in the time domain so that the optical signal has a polarization component around the polarization direction of the control pulse by optical parametric amplification; 
 an optical pulse generator to generate the control pulse and to provide the control pulse to said nonlinear optical medium; 
 a polarization controller, placed between said optical pulse generator and said nonlinear optical medium, to align a polarization direction of the control pulse to a designated angle relative to the polarization direction of the optical signal; and 
 a polarizer, placed on the output side of said nonlinear optical medium, having a polarization main axis orthogonal to the polarization direction of the optical signal, 
 an angle between the polarization direction of the optical signal and the polarization direction of the control pulse being between 40 and 50 degrees. 
 
     
     
       6. An optical waveform monitoring device, comprising:
 a first polarization controller to control a polarization direction of a phase-modulated optical signal or a frequency-modulated optical signal; 
 a nonlinear optical medium to which the optical signal output from said first polarization controller is input; 
 an optical pulse generator to generate a control pulse with a wavelength different from that of the optical signal and to provide the control pulse to said nonlinear optical medium; 
 a second polarization controller, placed between said optical pulse generator and said nonlinear optical medium, to align a polarization direction of the control pulse to a designated angle relative to the polarization direction of the optical signal; 
 a polarizer, placed at the output side of said nonlinear optical medium, having a main polarization axis orthogonal to a polarization direction of the optical signal output from said nonlinear optical medium; 
 an optical receiver to convert the output of said polarizer into an electrical signal; and 
 monitoring means for monitoring a waveform of the optical signal by tracing the electrical signal in a time domain, 
 the optical signal being selectively amplified with parametric amplification by the control pulse around a polarization direction of the control pulse in said nonlinear optical medium, a frequency of the control pulse being different from a bit rate of the optical signal, an angle between the polarization direction of the optical signal and the polarization direction of the control pulse being between 40 and 50 degrees.